#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
#pragma warning disable
using System;

using BestHTTP.SecureProtocol.Org.BouncyCastle.Crypto.Utilities;
using BestHTTP.SecureProtocol.Org.BouncyCastle.Utilities;

namespace BestHTTP.Connections.TLS.Crypto.Impl
{
    /// <summary>
    /// Implementation of Daniel J. Bernstein's ChaCha stream cipher.
    /// </summary>
    [BestHTTP.PlatformSupport.IL2CPP.Il2CppSetOption(BestHTTP.PlatformSupport.IL2CPP.Option.NullChecks, false)]
    [BestHTTP.PlatformSupport.IL2CPP.Il2CppSetOption(BestHTTP.PlatformSupport.IL2CPP.Option.ArrayBoundsChecks, false)]
    [BestHTTP.PlatformSupport.IL2CPP.Il2CppSetOption(BestHTTP.PlatformSupport.IL2CPP.Option.DivideByZeroChecks, false)]
    [BestHTTP.PlatformSupport.IL2CPP.Il2CppEagerStaticClassConstructionAttribute]
    public sealed class FastChaChaEngine
        : FastSalsa20Engine
    {
        /// <summary>
        /// Creates a 20 rounds ChaCha engine.
        /// </summary>
        public FastChaChaEngine()
        {
        }

        /// <summary>
        /// Creates a ChaCha engine with a specific number of rounds.
        /// </summary>
        /// <param name="rounds">the number of rounds (must be an even number).</param>
        public FastChaChaEngine(int rounds)
            : base(rounds)
        {
        }

        public override string AlgorithmName
        {
            get { return "ChaCha" + rounds; }
        }

        protected override void AdvanceCounter()
        {
            if (++engineState[12] == 0)
            {
                ++engineState[13];
            }
        }

        protected override void ResetCounter()
        {
            engineState[12] = engineState[13] = 0;
        }

        protected override void SetKey(byte[] keyBytes, byte[] ivBytes)
        {
            if (keyBytes != null)
            {
                if ((keyBytes.Length != 16) && (keyBytes.Length != 32))
                    throw new ArgumentException(AlgorithmName + " requires 128 bit or 256 bit key");

                PackTauOrSigma(keyBytes.Length, engineState, 0);

                // Key
                Pack.LE_To_UInt32(keyBytes, 0, engineState, 4, 4);
                Pack.LE_To_UInt32(keyBytes, keyBytes.Length - 16, engineState, 8, 4);
            }

            // IV
            Pack.LE_To_UInt32(ivBytes, 0, engineState, 14, 2);
        }

        protected override void GenerateKeyStream(byte[] output)
        {
            ChachaCore(rounds, engineState, x);
            Pack.UInt32_To_LE(x, output, 0);
        }

        /// <summary>
        /// ChaCha function.
        /// </summary>
        /// <param name="rounds">The number of ChaCha rounds to execute</param>
        /// <param name="input">The input words.</param>
        /// <param name="x">The ChaCha state to modify.</param>
        internal static void ChachaCore(int rounds, uint[] input, uint[] x)
        {
            if (input.Length != 16)
                throw new ArgumentException();
            if (x.Length != 16)
                throw new ArgumentException();
            if (rounds % 2 != 0)
                throw new ArgumentException("Number of rounds must be even");

            uint x00 = input[0];
            uint x01 = input[1];
            uint x02 = input[2];
            uint x03 = input[3];
            uint x04 = input[4];
            uint x05 = input[5];
            uint x06 = input[6];
            uint x07 = input[7];
            uint x08 = input[8];
            uint x09 = input[9];
            uint x10 = input[10];
            uint x11 = input[11];
            uint x12 = input[12];
            uint x13 = input[13];
            uint x14 = input[14];
            uint x15 = input[15];

            for (int i = rounds; i > 0; i -= 2)
            {
                x00 += x04; x12 = Integers.RotateLeft(x12 ^ x00, 16);
                x08 += x12; x04 = Integers.RotateLeft(x04 ^ x08, 12);
                x00 += x04; x12 = Integers.RotateLeft(x12 ^ x00, 8);
                x08 += x12; x04 = Integers.RotateLeft(x04 ^ x08, 7);
                x01 += x05; x13 = Integers.RotateLeft(x13 ^ x01, 16);
                x09 += x13; x05 = Integers.RotateLeft(x05 ^ x09, 12);
                x01 += x05; x13 = Integers.RotateLeft(x13 ^ x01, 8);
                x09 += x13; x05 = Integers.RotateLeft(x05 ^ x09, 7);
                x02 += x06; x14 = Integers.RotateLeft(x14 ^ x02, 16);
                x10 += x14; x06 = Integers.RotateLeft(x06 ^ x10, 12);
                x02 += x06; x14 = Integers.RotateLeft(x14 ^ x02, 8);
                x10 += x14; x06 = Integers.RotateLeft(x06 ^ x10, 7);
                x03 += x07; x15 = Integers.RotateLeft(x15 ^ x03, 16);
                x11 += x15; x07 = Integers.RotateLeft(x07 ^ x11, 12);
                x03 += x07; x15 = Integers.RotateLeft(x15 ^ x03, 8);
                x11 += x15; x07 = Integers.RotateLeft(x07 ^ x11, 7);
                x00 += x05; x15 = Integers.RotateLeft(x15 ^ x00, 16);
                x10 += x15; x05 = Integers.RotateLeft(x05 ^ x10, 12);
                x00 += x05; x15 = Integers.RotateLeft(x15 ^ x00, 8);
                x10 += x15; x05 = Integers.RotateLeft(x05 ^ x10, 7);
                x01 += x06; x12 = Integers.RotateLeft(x12 ^ x01, 16);
                x11 += x12; x06 = Integers.RotateLeft(x06 ^ x11, 12);
                x01 += x06; x12 = Integers.RotateLeft(x12 ^ x01, 8);
                x11 += x12; x06 = Integers.RotateLeft(x06 ^ x11, 7);
                x02 += x07; x13 = Integers.RotateLeft(x13 ^ x02, 16);
                x08 += x13; x07 = Integers.RotateLeft(x07 ^ x08, 12);
                x02 += x07; x13 = Integers.RotateLeft(x13 ^ x02, 8);
                x08 += x13; x07 = Integers.RotateLeft(x07 ^ x08, 7);
                x03 += x04; x14 = Integers.RotateLeft(x14 ^ x03, 16);
                x09 += x14; x04 = Integers.RotateLeft(x04 ^ x09, 12);
                x03 += x04; x14 = Integers.RotateLeft(x14 ^ x03, 8);
                x09 += x14; x04 = Integers.RotateLeft(x04 ^ x09, 7);
            }

            x[0] = x00 + input[0];
            x[1] = x01 + input[1];
            x[2] = x02 + input[2];
            x[3] = x03 + input[3];
            x[4] = x04 + input[4];
            x[5] = x05 + input[5];
            x[6] = x06 + input[6];
            x[7] = x07 + input[7];
            x[8] = x08 + input[8];
            x[9] = x09 + input[9];
            x[10] = x10 + input[10];
            x[11] = x11 + input[11];
            x[12] = x12 + input[12];
            x[13] = x13 + input[13];
            x[14] = x14 + input[14];
            x[15] = x15 + input[15];
        }
    }
}
#pragma warning restore
#endif
